Crane boom safety apparatus



June 4, 1963 Filed March 23, 1960 H. A. NESBIT CRANE BOOM SAFETY APPARATUS 4 SheetS -Sheet 1 *Q JA IVENTOK HaroldA-Nsbif BY fimawn ATTORNEY June 4, 1963 H. A. NESBXT CRANE BOOM SAFETY APPARATUS 4 Sheets-Sheet 4 Filed March 25, 1960 ATTORNEY June 4, 1963 H. A. NESBIT CRANE BOOM SAFETY APPARATUS 4 Sheets-Sheet 3 ZNVENTOR Har0ldA.N6sbi/i ZRFKM Filed March 23, 1960 A TTORNEY June 4, 1963 H. A. NESBIT CRANE BOOM SAFETY APPARATUS 10 m M M a QM EN. m M W H Q Filed March 23, 1960 A TTORNE Y United States Patent Office 3,092,261 Patented June 4, 1963 This invention relates to safety devices, and more particularly to safety equipment for preventing accidental damage to heavy construction equipment while in use.

Specifically, the invention relates to a safety attachment to a crane for retarding and stopping any material vertical reactive whipping movement of the boom caused by a sudden accidental release of a load suspended from the outer end of the boom.

As a general practice, the crane operator, when using a conventional crane for construction work, for example, drag line operations, locating girders and columns, etc., will move the crane to a suitable location, pivot the cab and boom horizontally to a selected position, and elevate the boom by the boom-hoist mechanism to the desired angular work position.

Whereupon, the boom having been raised to the desired elevation, the crane operator will place the boom-hoist machinery in neutral, or intermediate, to retain the boom at this angular position while the work is being performed. If the work includes raising and lowering loads, it is generally accomplished with the load hoist component of the crane, which includes a hook or attachment means fixed to the end of the load hoist cable and used for grasping the load, then raising or lowering the load relative to the boom.

In the event, however, a load suspended from the end of the boom is, for some reason, accidentally dropped or lost, for example, by the load hoist cable breaking or the hoist hook bending or fracturing under excessive weight, this sudden loss of a suspended load will create an equally sudden upward reactive-whip movement of the boom. If the whipping reaction is of suflicient magnitude, the boom may move upward and topple over backward onto the cab of the crane, resulting in possible complete destruction of the boom and cab and serious injury to the crane operator.

Since a conventional crane lacks means for preventing this upward reactive movement of the boom, several devices have been offered in the past to prevent accidents of this nature. However, none of these previous safety devices have been entirely satisfactory. For example, some devices lack means for immediately retarding the reactive movement of the boom, as soon as the suspended load is lost, so as to initiate the retarding action before the boom has an opportunity to pick up momentum; some devices have a tendency to interfere with rapid adjustment of the boom when being moved under the control of the boom hoist; certain others provide little more than an abrupt stop.

It is an object of this invention to overcome the difiiculties and deficiencies in existent devices, as well as provide an improved apparatus and method of preventing accidental damage to a boom crane, cab or operator during the crane operation.

Another object of the invention is to provide a novel apparatus for retarding and stopping the reactive-whip movement of a boom upon the sudden loss of its suspended load.

It is a further object of this invention to provide a safety attachment for a crane boom which will operate automatically, and which will not interfere with the normal use of the crane.

It is another object of this invention to provide a safety attachment for a crane which will gradually retard and stop upward movement of the boom upon a sudden loss of the boom load.

It is a further object of this invention to provide a safety attachment for a crane which will engage automatically when the boom has been positioned at a selected height.

An additional object of the invention is to provide a novel safety attachment for a boom which acts to automatically disengage when the boom is being moved or adjusted to a different selected height or work elevation,

and which automatically disengages in a manner so as to not impede the movement of the boom to the difierent height.

It is a further object of this invention to provide an apparatus that, when having completely stopped the reactive-whip movement of a boom acting under conditions of sudden loss of load, will retain the boom in its subsequent super-elevated position until the operator slowly releases the applied stopping power for eliminating damage to the crane structure, caused by the free-fall return of the boom to its previously determined working elevation.

Still another object of the invention is to provide a novel safety attachment to a crane which may be readily installed to a conventional crane and when installed will.

act, upon a sudden loss of a boom load, to retard the boom to a gradual stop within a relatively short arcuate length.

Other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevation of a conventional mobile crane with the crane boom-safety apparatus installed thereon and with the boom shown at two different elevations.

FIG. 2 is a top view of the crane boom-safety apparatus and a partial showing of the cab and boom of the crane, with the roof of the cab cut away to expose the hydraulic system and mechanical controls for operating the safety apparatus and the boom hoist.

FIG. 3 is a detailed fragmentary view of the crane boom and the channel and carriage assembly of the boomsafety apparatus with a portion of the cover panel of the channel cut away to expose the interior thereof.

FIG. 4 is a cut-away along line 4--4 of FIG. 3 disclosing the details of the interior of the carriage with its hydraulic cylinder and linkably connected brake shoes mounted thereon and the cooperating carriage guide and stop elements of the channel assembly.

FIG. 5 is a cut-away along line 5-5 of FIG. 3.

FIG. 6 is a cut-away along line 66 of FIG. 5 disclosing one of the carriage brake shoes and its mounting support.

FIG. 7 is a perspective view of the locking attachment for mounting the brake shoe.

FIG. 8 is a fragmentary view showing the directional valve for the hydraulic system and the control mechanism and linkage for operating the directional valve.

FIG. 9 is a fragmentary view showing the saddle block assembly mounted upon the crane gantry frame.

FIG. 10 is a schematic diagram of the hydraulic circuit.

Briefly stated, the invention comprises a hydraulically actuated crane boom retarding and stopping safety apparatus, which includes a boom channel member fixed along the boom, a carriage, slidable within the channel member, having hydraulically actuated brake shoes, frictionally engaging the boom channel walls, in response to the hydraulic system, to retard and stop any movement of the carriage relative to the boom channel and the boom, and a pivotal shock rod connecting the slidable carriage to the cab of the crane by means of a gantry for the retardin'g and stopping apparatus, which is operatively connected to the boom-hoist mechanism control lever, so as to automatically actuate the hydraulic system and quickly engage the brake shoes when the boom is stationary, and to automatically deactuate the hydraulic system to quickly disengage the brake Shoes when the boom is being adjusted to different heights by the use of the boom-hoist mechanism control lever, to thereby allow the boom to be moved or adjusted to different elevations rapidly and unhampered by the safety apparatus.

Referring more particularly to the drawings, .in FIG- URE l, a conventional mobile crane is shown in a simplilied illustration, with the crane boom safety apparatus or attachment mounted thereon. I

The mobile crane includes a cab 21, a chassis 22, a boom 23 with load-hoist cable 24 and boom-hoist cable 25 with pulleys 26 and 27 mounted at the outer end of the boom 23 for raising and lowering the hoist hook 28. The crane boom-safety apparatus is mounted to the crane with its boom channel member 30 attached to the top of the base section 29 of the boom 23. Channel 30 is held securely along the length of the boom by means of apluralityof C clamps 31. Within the channel 30 is located the slidable carriage 32 having a hydraulic cylinder 33 (see FIG. 4) for hydraulicallyactuating brake shoes 35 (FIG. 3). The brake shoes 35 are mounted upon the carriage 32 for frictionally engaging the side walls of the boom channel 30. At the outer end of the boom channel is a spring-mounted shock-absorbing apparatus 103 (FIG. 2). The shock rod 34 (see FIG. 1) is pivotally mounted at its one end 34 to the slidable carriage and pivotally mounted at the other end to a gantry frame 37 by means o f a sad- .dleblock 38, and is adapted to pivot about the gantry irame in response to the raising and lowering of the boom 23 while the carriage 32 is adapted to slide along the boom channel member 30.

. The boom is shown in two positions in FIG. 1 '(horizontal and vertical) to more clearly demonstrate the sliding or gliding action of the carriage from one end of the boom channel toward the other end when the elevation of the crane boom has been changed or adapted.

7 The hydraulic system of'the crane boom-safety appa ratus or retarding and stopping mechanism, the power drive and controls of the boom hoist, and the linkage mechanismoperatively connecting the hydraulic system to the boom hoist controls are best illustrated in FIG- URE 2.

In the figure, the boom-hoist'mechanism lever 50 is mounted to the floor of the cab and adapted by suitable linkage to control the axial movement of the clutch yoke or arm 46 along shaft 43 whichmoves the clutch 45 axially similarly toward and away from the load hoist drum 44. The movement of the lever 50 causes the clutch 45 and connectingclutch yoke 46 to move to any one of three positions. These positions are extreme right, in-

termediate, and extreme left with the extreme right, which is the closest positionof the clutch and yoke to the loadhoist drum, being the engaging position for powering the .boom upward, the intermediate position being for maintaining the boom'stationary, and with the extreme left ments old and well known to those versed in the art, the mechanisms are Simplified, to a certain extent, for clarity.

The crane engine 4% is mounted to the rear portion of the cab floor 41, with gear reduction and transmission drive 42 connecting the engine shaft 40' to the inner shaft 43, for rotatably driving the same. The shaft 43 extends along the axis of the load-hoist drum 44. The clutch 45 is located at the opposite end of the inner shaft.

When the boom-hoist clutch yoke 46 is in an extreme right position for powering the boom upward, the clutch 45 engages the rotating inner shaft to an outer shaft 47. 'lhisprovides power to drive the outer shaft 47, which in turn transmits power through a positive drive transmission 48 to the boom hoist drum 4-9 and rotates the boom hoist drum in a clockwise direction, when viewed from FIG. 1, acting to reel-in the boom hoist cables 25 and raise the boom. 7

When the boom-hoist clutch yoke 45 and clutch 45 are in an intermediate position, the clutch 45 disengages the inner shaft with the outer shaft and locks the outer shaft in a non-rotatable condition, and because of the positive drive connection between the outer shaft and the boomhoist drum, the boom-hoist drum and cable are accordingly held stationary.

Although in a conventional crane of the, military style, means are included to power the boom downward, in conventional civilian-style cranes, of the order being described, the boom is not powered downward. Rather,

when the boomrhoist clutch yoke is in an extreme left position the clutch 45 is released or disengaged from both the inner and outer shaft allowing the outer shaft and the boom hoist drum to notate freely, thereby enabling the boom to move downward as a natural gravitational reaction of its own weight, with the boom-hoist cable unreeling from the boom-hoist drum in response to the downward boom movement.

A foot-operated clutch brake (not shown) is generally used to limit and control the downward movement of the boom by engaging against the rim of the boom hoist drum. Clutch means, not shown, act to engage the outer sh-aft of the load-hoist drum for driving the load hoist :drum in one direction or the otherfor raising or lowering the load-hoist hook 28.

The boom-hoist clutch yoke 46 is connected to the Iorane boomsafety apparatus by linkage 54 (FIGS. 2 and vrelief valve 59 (FIG. 10) for regulating the pressure in the hydraulic system, a pump 58 providing the fluid pressure for operation of the hydraulic system, and a reservoir 57 with a supply of hydraulic fluid therein.

The hydraulic system as shown in FIG. 10 comprises broadly a means for actuating the hydraulic cylinder 33 in response to the directional valve 55.

The hydraulic pump 58 is connected by a suitable 'belt driving means to the crane engine 49. Accordingly, upon starting the engine 40 the hydraulic pump is energized and hydraulic fluid is pumped along fluid line 60 to the pressure-relief valve 59.

To provide cylinder pressure regulation, the bypass element of the pressure-relief valve operates to release "the excessive fluid pumped along line 60 into the relief valve 59 and bypass this excessive fluid back along line 61 to return it to the reservoir 57.

While the excessive fluid is being bypassed back into the reservoir or tank, the pressureaelief valve 59 allows the desired amount of hydraulic fluid to pass along fluid line 63 to the directional control valve 55.

When the directional valve rod 65 is in a downward projected position, resting in the hollow of the slide cam 54', as illustrated in solid lines in FIG. 8, which is its position when the hoist control lever is in neutral, the hydraulic fluid from line 63 (FIG. passes through the directional control valve 55 along valve passageway 66 which now connects with the fluid line 67 leading to the hydraulic cylinder 33. This applies fluid pressure to the hydraulic cylinder engaging the brake shoes at whatever pressure was selected by the adjustment of the bypass relief valve.

If the directional valve rod is depressed upward by movement of the cam 54 as illustrated in dashed lines in FIG. 8, or in other words when the boom-hoist clutch yoke is either in the extreme right or extreme left position as illustrated in dashed lines in FIG. 8, the hydraulic fluid from line 63 passes through the directional control valve along valve passageway 68 and back along the fluid line 67 to the tank while the hydraulic pressure in the cylinder 33 is released along fluid passage 68 for deactuating the cylinder and for disengaging the brake shoes.

Mounted rigidly upon the cab, is the gantry frame 37 (FIG. 1) which consists of two pairs of upwardly converging stanchions (70, 71, 72 and 73) (FIG. 2). The stanchions are connected together at their upper ends by pins 74 and 75, with a supporting rod 76 extending transversely across from one pair of stanchions to the other.

A saddleblock assembly 38 (FIG. 9) comprising a pair of rectangular bars 78 and 79 with each having an opposed semi-cylindrical recess for embracing the support rod 76, is pivotally mounted about rod 76 by means of pins 80.

The shock rod 34 (FIG. 9) of the safety apparatus is rigidly mounted to the saddle block by means of an annular flange 81 to enable the shock rod to rotate about the axis of the support rod 76 upon the saddle blocks pivotal mountings.

The crane boom is pivotally attached to the cab by means of supporting arms 82 and 83 (FIG. 2), which arms at their respective remote ends 84 and 85 have eye openings for receiving bolts 86 and 87. Upright mountings 88 and 89 have flanges emcompassing the opposite sides of the remote ends 84 and 85 of the boom and act to receive the bolts 86 and 87 for supporting the boom in pivotal relationship. At the other end of the uprights 88 and 89 is a similar pair of eye openings and bolts 90 and 91 for mounting the forward pair of stanchions of the gantry frame .to the floor of the cab.

The hydraulic line 67, which provides the hydraulic fluid connection between the hydraulic system located on the cab of the crane and the hydraulic cylinder on the boom of the crane to actuate the brake mechanism, travels from the directional control valve upward through an opening 92. in the shock rod 34 immediately adjacent the saddle block assembly and runs along the hollow interior of the shock rod toward the boom and passes out through another opening 93 in the shock rod 1mrnediately adjacent the slideable carriage mounted on the boom. The line 67 thereupon extends into the carriage and terminates in fluid communication with the hydraulic cylinder mounting 94 of the hydraulic cylinder 33.

In FIG. 3, a more detailed showing of the carriage and boom channel member of the safety apparatus is set forth. These two components of the safety apparatus, located along the length of the boom, cooperate together to perform the retarding and stopping functions of the invention. The cover 95 of the channel member is cut away to expose the details of the slidable carriage and the facilitating supports of the channel member. Channel 30 comprises a pair of parallel carriage tracks 96 and 97 running along the base 98 of the channel for supporting and guiding the sliding action of the carriage. A

pair of upright side wall members 99 and 100 are mounted upon opposite sides of the base of the channel, having inner surfaces 101 and 102 olfering a continuous frictional engaging surface for the brake shoes 35 and 35 of the carriage as it moves along the channel.

At the outer remote end of the channel 30 is a springmounted shock absorbing assembly 103 which provides a cushioning abutment means for the carriage when it approaches the end of the carriage tracks 96 and 97. The shock absorbing assembly 103 comprises a pair of rods 104 and 105 extending toward the carriage and along the path of the carriage tracks. A pair of springs 106 and 107 longitudinally encircle the rods and a bumper plate 108 is fixedly mounted at the outer pro jection of the rods. The rods are adapted to slide through bearing openings 109 and 110 of the end wall 111 of the channel. When pressure is applied to the bumper plate, the springs tend to resist the sliding action of the rods and maintain the rods biased outwardly, as

illustrated.

The slidable carriage of the safety apparatus, in more detail (see FIGS. 3, 4, and 5), comprises a container housing 112 which includes a base plate 113, a pair of opposed Walls 114 and 115 and a top panel 116. Mounted to the carriage is the hydraulic cylinder 33 which is adapted to move the ram 117 outwardly under hydraulic pressure. At the outer end of the ram is a clevis 118. A pair of opposed expansion linkages 119 and 120 are pivotally connected to the clevis 118 at their one end by means of a pin 121, and are pivotally attached at their other ends by means of similar pins 122 and 123 to a pair of axially slidable brake shoe rams 124 and 125. The brake shoe rams 124 and 125 are supported by a pair of sleeve bearings 126 and 127 for movement laterally in response to the movement of the hydraulic cylinder ram 117 in a direction toward and away from the boom channel side walls 99 and 100.

At the outer ends of the brake shoe rams are attached a pair of rectangular brake shoes 35 and 35' which act to frictionally engage the channel side walls 99 and 100 when the hydraulic cylinder is actuated, forcing the cylinder ram outwardly.

The frictional engaging surfaces of the brake shoes are preferably made of high grade cast-iron, cast in a manner to attain a high degree of smoothness, free of pockets, projections, and imperfections, so as to prevent gaulding of the brake shoe surfaces with the side walls of the boom channel. FIGS. 4 and 5 which provide longitudinal and transverse sectional disclosure of the carriage and boom channel disclose further details, particularly as to the guiding track structure of the channel and the cooperating base portions of the carriage. The carriage has a tongue 128 mounted in spaced relation to the carriage base plate 113, with the tongue, substan tially coextensive in length with the carriage and projecting laterally on opposite sides toward the side walls of the boom channel.

A pair of elongated Z shaped groove forming angle bars 129 and 130 are mounted in opposed relation along the base of the channel cooperatively receiving and retaining the tongue 128 therein in sliding relation. The carriage tongue 128 has a pair of soles 131 and 132 mounted on its underside for properly aligning the carriage tongue to the Z shaped grooves of the channel. The Z shaped angle bars 129 and 130 are rigidly mounted to the floor 133 of the channel by means of a plurality of bolts 134 and 135. The floor 133 of the channel, in turn, is rigidly secured to the base support 136 of the channel by spot welding 137 and 138 where the channel walls and channel base plate intersect one another. The base support of the channel is rigidly secured to the boom along its outer edges 140 by means of C clamps 31 which clamp the upper angle bars 139 of the boom to the base support edges 140.

FIGS. 6 and 7 disclose the manner of mounting and looking the brake shoes to the brake shoe rams by means of an annular collar 141 having a plurality of space bolts 142 extending through the collar and rigidly connected to the brake shoe with an L shaped strap 144 locking the shoes to the ram. The L shaped strap 144 engages a key way 145 in the brake shoe ram by means of a tongue 146 at one end of the strap. 'The other end of the strap has an eye opening 147 mounted to one of the bolts 142 extending through the collar 141 The operation of the crane boom safety apparatus is substantially as follows: when the crane operator is raising or lowering the boom by movement of the boom hoist. control lever, initiating .movement of the boom hoist clutch yoke to the extreme right position or extreme left position, the hydraulic cylinder of thecrane boom safety apparatus is automatically deactuated .and consequently the hydraulic cylinder ram is withdrawn or retracted and the brake shoes are disengaged from the walls of the channel mounted to the boom. This enables the carriage to slide freely up and dow'n'the channel as the boom correspondingly moves upward and downward.

i However, when the crane operator moves -,the hoist :control lever into neutral for holding the boom stationary at some selected work elevation, the hydraulic system automatically actuates the cylinder and projects the hy-' jdraulic cylinder ram causing the .brake'shoes to engage 'boom hoist cables, and when'the 'crane operator moves the boom hoistlever backward the boom 'hoi'st clutch yoke is moved to an extreme right position which moves the clutch 45 axially toward the load hoist drum 4.4. V

This movement, with respect to a "conventionalicrane mechanism, causes the clutch 45 to engage the 'driveito the boom hoist drum by connecting the inner shaft '43, which is being rotatably driven by the crane engine, to the outer shaft 47. This engagement causes simultaneous rotation of the outer shaft 47, which in turn drives the boom hoist'drum49 winding in the boom hoist cable and drawing'the boom upward.- V The movement of the boom hoist clutch 45, on the "other hand, simultaneously deactuates the crane boom safety apparatus by moving the camslide 54- to its extreme right position whichdepresses the valve rod 65 of the directional control valve. This rod 65 has three independentfluid passages, 66, 68, 68', which .willlcommunicate with the exterior lines whenipositioned. The depressing slide movement of the rod 65 bypasses the oil :pressure from line 63 throughthe valve passage 68 along line 67' back to the storage tank, blocks the diagonal passage 66 from communicating with line {63 and releases the oil pressure in the hydraulic cylinder by allowing the oil to flow through valve passage 68 back along line 6 4 'tothetank. V f

Therele'ase of the 'oil pressure in the hydraulic cylinder 33 causes the cylinder ram to'immediately begin returning into the cylinder which withdraws'the brake shoes 35 and 35' from against the walls of the channel assembly of the crane b'oom thus enabling the carriage 32 to slide *freely and unrestrained upward along the channel assem- -bly,*witho"ut impeding theboom travel, as the boom hoist cable's begin to raise the boom upward.

Had the crane operator, instead decided to move the,

vboom downw'ardly,the operationwould have begun-by rnoving the boom hoist lever forward thereby moving the boom-hoist clutch'yoke to the extreme left position which moves the clutch 45 outwardly from the load hoist drum,

and with respectto .the crane mechanism, causes the drive pulls the slide cam 54' to its extreme left position which similarly acts to depress the rod 65 of the directional control valve. This causes the oil pressure to the hydraulic cylinder to be bypassed, thereby releasing the brake shoes from against the channel assembly and allowing the carriage of the safety apparatus to slide freely along thechannel assembly as the boom moves down.

When the boom has reached its desired angular work elevation, by either movement upward or downward, the operator pivots the boom hoist control into neutral which brings the boom to a stop and holds it stationary, by the clutch 45 holding the outer shaft stationary which in turn holds the boom hoist drum stationary thus preventing the boom hoist cables from reeling in or out. 7

The movement of the hoist control lever into neutral position automatically actuates the safety apparatus as it moves the clutch 45 into neutral which in turn moves the slide cam 54 into its neutral position. This allows the rod 65 of the directional control valve to projectinto the hollow of the slide. rod, which may be encouraged by suitable biasing, cuts off the flow of fluid pressure past the valve along passage 68, thus preventing it from returning to the tank and forces the desired fluid pressure to flow through the diagonal valve passage 66 into line 67 to the hydraulic cylinder while it also blocks off the cylinder release line 64 back to the tank, by moving valve, passage 68' out of communication therewith. This actuates the hydraulic cylinder by forcing the cylinder ram outward, and the outward movement of the ram, moves the brake shoes, in opposite directions, into frictional engagement against the walls of the channel assembly.

The brake shoes continuously engage the channel walls as long as the crane engine is running and the hoist lever is in neutral, since this pump provides continuous fluid pressure into the cylinder.

The brake shoes of the safety apparatus, although they are frictionally engaging the channel assembly of the boom and act to hold the boom at that angle, then will, however, slide along the wall of the channel assembly if an excessive amount of pressure is applied against the boom.

Thus, when the crane operator places the boom at its desired elevation, automatically actuating the safety apparatus, and proceeds with such crane operations as girder placement or others requiring the use of the load hoist for raising and lowering heavy objects from the end of the boom, should the suspended load he suddenly released, thereby creating a strong upward reactive whip movement of the boom, and this reaction be of sufiicient violence, it will overcome the frictional force of the brakes and the carriage will slide a relatively short distance with respect to the length of the channel before the brakes sufliciently retard the whip movement of the boom to bring the boom to a stop.

This sliding retarding efiect or give thereby prevents any damage to the boom which might result if'an abrupt stop device were used to overcome a violent whip reaction, as an abrupt stop may result in the boom merely The projecting movement of the to a complete stop by the brake shoes of the carriage assembly within a minimum arcuate movement of the boom without damage.

In the normal use of a boom of a conventional crane, the boom may on occasion be raised to nearly 90 degrees upward or vertical or lowered to approximately horizontal. Since the carriage slides along the length of the boom in response to the raising or lowering of the boom, the channel member (as seen in FIG. 1), to accommodate this movement, is provided with ample length to assure that the carriage remains within the channel member and has continuous and supporting guideway as well as wall engaging surfaces for its brake shoes anywhere within this operating range.

This enables the safety apparatus to immediately begin retarding the upward whip reaction the moment the boom starts to move, regardless of the working angle the boom may have been adjusted to, within this operating range, as the brake shoes may engage against the channel walls for immediate effective retarding wherever the carriage is located along the length of the channel.

This feature is of importance in that it begins to stop the reactive movement of the boom before the boom acquires momentum.

Because of the automatic features of the safety apparatus no conscious effort is required on the part of the crane operator for placing the safety device into operation at the appropriate times, as the safety device automatically respond to the hoist control lever, and accordingly while the boom is stationary it will automatically engage as a retarding and stopping apparatus.

The safety device engages and disengages practically instantaneously because of the relatively short stroke of the hydraulic cylinder necessary to move the brakes in and out of engagement with the walls of the channel. This action is also very rapid because the pump of the hydraulic system is constantly in operation whenever the crane engine is on, providing an immediately available source of hydraulic pressure for actuation of the cylinder.

Furthermore, because of the rapid engagement and disengagement of the safety apparatus, it does not impede rapid adjustment of the boom to different elevations, as the brake shoes lose most of their efiectiveness the instant the pressure drops and disengage before the boom has started to move, needing physically only a fraction of an inch movement for disengagement. The carriage may thereafter slide freely.

The upward movement of the boom is limited to approximately 88 /2 degrees. At this elevation the carriage engages the spring cushion at the upper end of the channel. This acts as a safety precaution to prevent the operator from, inadvertently, allowing the boom to accidentally be raised by the boom hoist to such a near vertical position that wind currents or possibly the inertia from raising of the boom might cause the boom to fall backward over onto the cab. If desired, however, the stop could be adjusted to allow the boom to move even closer to a vertical position.

The brake shoes of the safety apparatus provide sufficient pressure against the channel walls to hold the boom at its angular elevation independently of the boom hoist cables, or in other words should the boom hoist cables be released or become loose for some reason, the boom will not fall to the ground. They further provide sutiicient pressure to retard and stop the downward movement of the boom, under the loading of its own weight.

This is of importance, in that it has sometimes happened in the past that a crane boom has lost its hoist load causing the boom to move reactively upward to only a near vertical position, hesitate and fall back down toward the front of the cab; and upon falling back down toward the front of the cab, the boom has torn the boo-m hoist cables and mountings completely out of the cab when the cables became taut, and has caused damage to the boom and other associated parts as well.

Since the safety apparatus provides suificient hydraulic braking power to the brake shoes to retard the boom in either direction as well as hold it at its adjusted elevation independently of the hoist cables, such a reaction as just described would be brought to a stop by the safety apparatus before any damage of that nature would be done.

The safety device may be quickly attached or removed from a conventional crane with only a minimum number of tools, installation work and time required. The channel and carriage assembly are simply but securely mounted to the bottom by means of C clamps, while the hydraulic system and shock rod and saddle block assembly may be installed on the cab by merely bolting them to the cab floor and gantry frame respectively.

The oil pump pressure of the safety apparatus may be regulated by the relief valve so as to adjust the force of engagement of the brakes, depending upon the length of boom being used on the crane. Since a greater amount of braking pressure is necessary in a longer boom than on a short boom, it is important that the pressure be regulated so that sufiicient braking action will be available for various different lengths of booms used. It has been found that a range of from 500 psi. to 2,000 p.s.i. will provide a satisfactory operating range for most boom lengths.

To assist the operator in selecting the appropriate hydraulic pressure for a particular length of boom a hydraulic pressure chart may be attached to the cab of the crane which will set forth the necessary pressure required for any given length of boom so that should the operator decide to add an extension to the boom to increase the length of the boom for 10 to 20' feet, for example, he would merely glance at the chart and adjust the relief valve to the pressure to suit the length of the boom chosen.

While a conventional boom hoist mechanism, patterned after a standard civilian style crane, has been briefly described in connection the operation of the safety apparatus invention, it has been only to illustrate the manner in which the safety apparatus responds to the boom hoist lever. The military cranes, such as used by the US. Army Corps of Engineers, also employ a hoist lever movement identical with that described herein. It should be understood, however, that the invention is readily adapted to various types of cranes, even though the specific type of boom hoist lever movement and mechanism varies considerably .from that described.

It will be obvious to those schooled in the art that various changes may be made in this invention without departing from the spirit and scope thereof, and therefore this invention is not limited by that which is shown in the drawings or described in the specification but only as indicated in the accompanying claims.

What is claimed is:

l. A crane boom retarding and stopping device cornprising a cab and a boom pivotally mounted to said cab, a rail assembly, said rail assembly including a pair of opposed side walls, a base connecting said pair of side walls, and means connecting said rail assembly to said boom, a carriage slidably mounted along the length of said boom and said rail assembly, guide means within said rail assembly adapted to guide said carriage along the length of said rail assembly, brake shoes mounted and in opposite relation to one another and adapted to engage the opposed wall members of said rail assembly, hydraulic pressure means mounted on said carriage and adapted to force said brakes into engagement with the wall members of the rail assembly, a shock rod member, the carriage having a pivotal mounting along its upper surface and adapted to pivotally receive one end of said shock rod member, a triangular gantry member fixedly mounted to the cab of said crane and having a transverse support bar with mounting means located centrally of said support bar, said mounting means being adapted to engage the other end of said shock rod whereby said shock rod may pivot about the axis of transverse member of the gantryframe, hoist means for raising and lowering said boom along a vertical plane, hydraulic actuating means responsive to said hoist means whereby when said boom is being maintained stationary at a selected vertical position said hydraulic actuating means will act (to apply pressure to said hydraulic pressure means for engagement of the brake shoes to the rail assembly of the boom 7 ,for supporting the boom at said selected vertical position, said hydraulic actuating means being adapted to respond to the hoist means whereby when the hoist means is engaged for moving the boom upwardly or downwardly :the

brake shoe engagement is disengaged by the release of the hydraulic pressure, a spring cushion means mounted at the upper end of said rail assembly to provide a remote cushion stop for said carriage movement.

2. A crane boom retarding stop device for attachment to the cab and boom of a "crane comprising channel means along the length of said boom, carriage means adapted to move longitudinally within the confines of said channel,

,boom hoist means for raising and lowering a boom and load hoist means for raising nad lowering objects from one end of said boom, a safety device adapted to be attached to said crane comprising guideway means along the length of the boom, carriage means for movement lengthwise along the boom and along 'a path :defined by said guideway means, pivotal means connecting said carriage to said cab, actuating means on said carriage adapted to fricti onally engage said means along the length of said boom to retard any sudden accidental movement-oi the boom, means for disengaging said frictional engaging .means whereby said boom hoist means may operate to move the boom upwardly or downwardly rapidly Without interference by said frictional engaging means.

4. A crane including a cab having a boom projecting outwardly from one end of said cab, means mounted to portions of said boom, retarding means connected to said cab and movable along said boom, said retarding means being adapted to releasably engage said means mounted to portions of said boom for frictionally stopping any sudden accidental movement of said boom while the 1 boom is being maintained at a stationary angle, means tor moving said boom to different angular positions,

means cooperating with said moving means to disengage said retarding means while moving the boom to different elevations, to thereby allow said boom to move unimpeded by said retarding means.

' 5. A boom retarding and stopping device for a boom adapted to be raised and lowered and held stationary at 12 mounted at its one end to said cab, connecting means mounted to the cab with its one end extending toward the boom, hydraulically actuated retarding and stop'means mountedgat said one end of the connecting means and means mounted on said boom and connected to said connecting means in sliding relation, said retarding :and stop means having hydraulically actuated brake shoe means laterally engaging said connecting means to said means mounted on said boom in a manner to retard and stop any movement of the boom in either direction and slidably adjustable for engaging the boom at any angle it may be positioned, within its normal operating limits, so as-to immediately begin to retard and stop the boom movement the moment the boom movement begins.

'7. The structure of claim 6 in which additional safety means comprising cushioning means are mounted to the boom to bring theboom :to a positive stop at slightly less .than a vertical position to provide an upper limit to the boom movement.

8. The combination of a frame, a boom pivotally mounted at its one end to said frame and adapted to be positioned at difierent selected vertical angles, connect- 5 ing means mounted to the frame and extending toward the boom, retarding and stop means mounted at said one end of the connecting means on the boom and fluid actuated for engaging the boom to retard and stop any movement of the boom While positioned at a desired angle,

and adjustable means for said retarding and stopping means whereby the retarding and stopping means may immediately begin to retard and stop any movement of the boom, regardless of the vertical angle selected.

9. A crane boom retarding stop device for attachment to the cab and boom of a crane comprising straight elongated channel means extending generally parallel along the length of said boom, carriage means adapted to move longitudinally of the channel means within the confines of said channel means, pivotal means connecting said carriage to said cab, hydraulic brake means mounted to said carriage and adapted to laterally engage said channel means, said brake means including a hydraulic cylinder and at least one brake shoe, with linkage connecting said cylinder to said shoe, for engaging said shoe to said channel upon actuation of said cylinder, whereby when said shoe engages said channel the boom will be retarded and stopped from movement relative to said carriage and said cab.

10. A crane boom retarding and stop device for attachment to the cab and boom of a crane comprising a straight elongated guideway means extending longitudinal along the length :of the boom, carriage means adjacent the boom movably mounted to said guideway means for longitudinal travel along said guideway means, pivotal means connecting said carriage means to said cab, fluid actuated References Cited in the file of this patent UNITED STATES PATENTS l Sathre et a1. Feb. 10, Kahl Dec. 29, 195 

1. A CRANE BOOM RETARDING AND STOPPING DEVICE COMPRISING A CAB AND A BOOM PIVOTALLY MOUNTED TO SAID CAB, A RAIL ASSEMBLY, SAID RAIL ASSEMBLY INCLUDING A PAIR OF OPPOSED SIDE WALLS, A BASE CONNECTING SAID PAIR OF SIDE WALLS, AND MEANS CONNECTING SAID RAIL ASSEMBLY TO SAID BOOM, A CARRIAGE SLIDABLY MOUNTED ALONG THE LENGTH OF SAID BOOM AND SAID RAIL ASSEMBLY, GUIDE MEANS WITHIN SAID RAIL ASSEMBLY ADAPTED TO GUIDE SAID CARRIAGE ALONG THE LENGTH OF SAID RAIL ASSEMBLY, BRAKE SHOES MOUNTED AND IN OPPOSITE RELATION TO ONE ANOTHER AND ADAPTED TO ENGAGE THE OPPOSED WALL MEMBERS OF SAID RAIL ASSEMBLY, HYDRAULIC PRESSURE MEANS MOUNTED ON SAID CARRIAGE AND ADAPTED TO FORCE SAID BRAKES INTO ENGAGEMENT WITH THE WALL MEMBERS OF THE RAIL ASSEMBLY, A SHOCK ROD MEMBER, THE CARRIAGE HAVING A PIVOTAL MOUNTING ALONG ITS UPPER SURFACE AND ADAPTED TO PIVOTALLY RECEIVE ONE END OF SAID SHOCK ROD MEMBER, A TRIANGULAR GANTRY MEMBER FIXEDLY MOUNTED TO THE CAB OF SAID CRANE AND HAVING A TRANSVERSE SUPPORT BAR WITH MOUNTING MEANS LOCATED CENTRALLY OF SAID SUPPORT BAR, SAID MOUNTING MEANS BEING ADAPTED TO ENGAGE THE OTHER END OF SAID SHOCK ROD WHEREBY SAID SHOCK ROD MAY PIVOT ABOUT THE AXIS OF TRANSVERSE MEMBER OF THE GANTRY FRAME, HOIST MEANS FOR RAISING AND LOWERING SAID BOOM ALONG A VERTICAL PLANE, HYDRAULIC ACTUATING MEANS RESPONSIVE TO SAID HOIST MEANS WHEREBY WHEN SAID BOOM IS BEING MAINTAINED STATIONARY AT A SELECTED VERTICAL POSITION SAID HYDRAULIC ACTUATING MEANS WILL ACT TO APPLY PRESSURE TO SAID HYDRAULIC PRESSURE MEANS FOR ENGAGEMENT OF THE BRAKE SHOES TO THE RAIL ASSEMBLY OF THE BOOM FOR SUPPORTING THE BOOM AT SAID SELECTED VERTICAL POSITION, SAID HYDRAULIC ACTUATING MEANS BEING ADAPTED TO RESPOND TO THE HOIST MEANS WHEREBY WHEN THE HOIST MEANS IS ENGAGED FOR MOVING THE BOOM UPWARDLY OR DOWNWARDLY THE BRAKE SHOE ENGAGEMENT IS DISENGAGED BY THE RELEASE OF THE HYDRAULIC PRESSURE, A SPRING CUSHION MEANS MOUNTED AT THE UPPER END OF SAID RAIL ASSEMBLY TO PROVIDE A REMOTE CUSHION STOP FOR SAID CARRIAGE MOVEMENT. 